1. Field of the Invention
The present invention relates to a method for servicing a live pipeline. More particularly, the present invention relates to a method which is suitable for servicing a live pipeline which minimizes or eliminates service interruption and contamination.
2. Description of the Prior Art
A pipeline is live when it is carrying a fluid such as gas, liquid, slurry, or vacuum. Servicing live pipelines to make repairs or to install new components or branch sections or other extension sections presents difficulties due to the presence of the fluid being carried by the pipeline. Not only does the escape of the fluid itself cause many problems, but the fluid also interferes with the installation of the replacement sections or components and can affect the integrity of the connections made during the servicing activity.
The difficulties are particularly acute when such a live pipeline being serviced is part of a system which is sensitive to contamination, e.g., a medical gas distribution system in a hospital. Such pipelines are subject to rigorous codes to insure the cleanliness and the integrity of the distribution system and of the delivered fluid. For example, under the National Fire Protection Association (NFPA) Code 99-1996, which is applicable to hospitals, pipelines carrying such medical gases as oxygen, air, nitrogen, and nitrous oxide, as well as vacuum, may only be made of copper and, with few exceptions, all connections must be made by soldering or brazing or by memory-metal couplings having temperature and pressure ratings not less than that of a brazed joint.
A variety of schemes and special devices have been devised in the past for servicing live pipelines, but there has not yet been developed a quick and simple method having general applicability which results in a pipeline meeting the high integrity and cleanliness required for medical gas distribution piping. Some existing methods, such as those described in Yano et al., U.S. Pat. No. 4,527,586, issued Jul. 9, 1985 or Saha et al., U.S. Pat. No. 5,577,528, issued Nov. 26, 1996 require the temporary installation of work enclosures sealed around the pipeline. Others, such as those described in Gardner, U.S. Pat. No. 3,867,964, issued Feb. 25, 1975 or Minotti, U.S. Pat. No. 4,351,349, issued Sep. 28, 1982 or Smith, U.S. Pat. No. 4,355,656, issued Oct. 26, 1982 or Jiles, U.S. Pat. No. 5,052,431, issued Oct. 1, 1991 require affixing special fittings which remain attached to the pipeline after the servicing operation has been completed. Others, such as those described in Ray, U.S. Pat. No. 3,773,067, issued Nov. 20, 1973 or Rockower et al., U.S. Pat. No. 4,869,281, issued Sep. 26, 1989 require the preexistence in the pipeline of a plugged T-connection or other component through which the interior of the pipeline can be accessed. Others, such as that described in Struder et al., U.S. Pat. No. 4,508,130, issued Apr. 2, 1985 require the preexistence in the pipeline of a shutoff valve upstream of the location that is to be serviced. Some, such as that described in the above mentioned Minotti result in the pipeline having components and connections which would not meet the above mentioned NFPA code.